Normal paraffin alkylation with a catalyst of a Lewis acid and group VIII metal intercalated in graphite

ABSTRACT

Normal paraffin alkylation with an alkylating agent, i.e. olefin, alkylhalide or alcohol, is effected in the presence of a catalyst of graphite having intercalated in the lattice thereof between about 5 and about 75 weight percent of a Lewis acid. The catalyst utilized in alkylation has additionally intercalated therein between about 0.1 and about 20 weight percent of a Group VIII metal.

CROSS REFERENCE TO RELATED APPLICATION

This application is a division of application Ser. No. 467,316 filed May6, 1974, now U.S. Pat. No. 3,925,495 which issued on Dec. 9, 1975.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the conversion of hydrocarbons in the presenceof a unique catalyst in which active catalytic sites are intercalated inthe lattice of graphite.

2. Description of the Prior Art

It has heretofore been known to accomplish the conversion ofhydrocarbons in the presence of a wide variety of catalysts includingthose in which the active catalytic component is deposited on a porousinert support such as, for example, graphite. U.S. Pat. No. 3,678,120describes such process in which the catalyst employed is a porous inertsolid support having deposited thereon a catalytic complex of anantimony pentafluoride component and a hydrogen fluoride or afluorosulfonic acid component. It has been reported in U.S. Pat. No.3,708,553 that hydrocarbon conversion and more specifically alkylationcan be carried out in the presence of a catalyst of a Lewis acid such asantimony pentafluoride combined with a Bronsted acid such asfluorosulfuric acid. The intercalation of various salts in the latticeof graphite has previously been described. Thus, it has been reported inJ. Chem. Soc., Chem. Comm., 21, 815(1973) that intercalation of antimonypentafluoride in the lattice of graphite is accomplished by heating amixture of SbF₅ and graphite at 110°C. for a few days. In none of thisprior art, which is the most relevant known, is there any recognition ordisclosure of utilizing a catalyst in which active catalytic sites areintercalated within the lattice of graphite.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a catalyticprocess for converting hydrocarbons in the presence of a heterogeneouscatalyst consisting essentially of graphite having intercalated thereina Lewis acid of the formula MX_(n) where M is an element selected fromGroup II-A, III-A, IV-B, V or VI-B of the Periodic Table, X is a halogenand n is an integer of from 2 to 6. In one embodiment of the invention,the catalyst may additionally have intercalated in the graphite aBronsted acid such as hydrofluoric acid, hydrochloric acid,fluorosulfuric acid or trifluoromethane-sulfonic acid and mixturesthereof. In another embodiment of the invention, thegraphite/intercalated Lewis acid composite may have a Group VI-B orGroup VIII metal additionally intercalated in the graphite to provide ahighly effective catalyst for the conversion of hydrocarbons includingisomerization, polymerization, cracking and alkylation.

The graphite utilized in the present catalyst is desirably characterizedby a surface area of about 0.3 to about 50 m² /gram; a typical graphiteapplicable for use in the present invention is characterized by thefollowing properties:

Surface Area of 0.46 m² /gram

Real Density of 2.16 gram/cc

Particle Density of 1.90 gram/cc

Pore Volume of 0.065 cc/gram

Lewis acids suitable for use in the catalysts employed in the presentinvention include the Group II-A, III-A, IV-B, V and VI-B halides.Representative of such compounds are vanadium pentafluoride, borontrifluoride, aluminum chloride, niobium pentafluoride, tantalumpentafluoride, ferric chloride, antimony pentafluoride, titaniumtetrafluoride, bismuth pentafluoride, molybdenum hexafluoride, berylliumchloride, zirconium tetrafluoride, arsenic pentafluoride and phosphoruspentafluoride. In addition to the fluorides, the chlorides, bromides oriodides may be employed. The amount of Lewis acid intercalated in thelattice of graphite is generally between about 5 and about 75 weightpercent and preferably between about 10 and about 60 weight percent.

When a Bronsted acid, such as hydrofluoric acid, hydrochloric acid,fluorosulfuric acid or trifluoromethane-sulfonic acid is alsointercalated in the graphite lattice, the amount thereof is generallybetween about 0.5 and about 75 weight percent and preferably betweenabout 1 and about 50 weight percent, with the molar ratio of Bronsted toLewis acid being within the range of 0.1:1 to 50:1 and more particularlyin the range of 0.1:1 to 5:1.

When a Group VI-B or Group VIII metal is additionally intercalated inthe graphite, the amount employed is such as to afford a resultingcomposite containing between about 0.1 and about 20 weight percent ofthe metal. With metals of the platinum group, the amount of metal ispreferably in the approximate range of 0.1 and 5 weight percent. Othermetals contemplated for intercalation include nickel, cobalt, iron,chromium, molybdenum and tungsten. Particularly preferred are the GroupVIII metals, especially platinum and palladium.

Intercalation of the Lewis acid in the lattice of the graphite isreadily effected by heating a mixture of graphite and the Lewis acid,generally in the presence of chlorine, at a temperature between about80° and 150°C., preferably at approximately 110°C. for a period ofbetween about 1 and about 72 hours. When a metal of Group VI-B or GroupVIII is also desired in the catalyst, intercalation is achieved byheating a compound of the appropriate metal with graphite, preferably inthe presence of chlorine, at a temperature within the approximate rangeof 100° to 200°C. for a period of between about 4 and about 24 hours.The intercalated metal compound is then reduced, generally with flowinghydrogen, at a temperature of about 300° to about 400°C. for a period ofapproximately 8 to about 24 hours. Thereafter, intercalation of thedesired Lewis acid into the metal/intercalated graphite composite may beeffected as described above. In similar fashion, when a Bronsted acid isadditionally desired in the catalyst, such acid may be intercalatedafter intercalation of the Lewis acid into the lattice of the graphite.Intercalation of the Bronsted acid is achieved by heating the graphitewith such acid at a temperature between about -40°C. and about 100°C.for a period of between about 1 and about 5 hours. It is also feasibleand, in some instances preferable, to intercalate both (1) a metal ofGroup VI-B or Group VIII and (2) a Bronsted acid into the lattice of thegraphite having Lewis acid intercalated therein. In such embodiment, thegraphite is treated to introduce the Group VI-B or Group VIII metal, asdescribed above, followed by intercalation of the Lewis acid under theconditions specified hereinabove, and then intercalation of the Bronstedacid as described.

A wide variety of hydrocarbon conversion reactions may be effectedutilizing the present catalyst. Such conversion processes include thosecatalyzed by the presence of acidic sites such as cracking,isomerization, alkylation, polymerization, disproportionation,dealkylation, transalkylation and similar related processes. Theseprocesses are effected by contacting a hydrocarbon or hydrocarbonmixture with the above-described catalyst at hydrocarbon conversionconditions. The catalyst to hydrocarbon weight ratio employed isgenerally between about 1:5 and about 1:20. The temperature employed isgenerally between about 0° and about 650°C. Contact between the catalystand hydrocarbon charge may take place utilizing any of the conventionalsystems such as a fixed bed system, a moving bed system, a fluidized bedsystem or a continuous or batch-type operation. The hydrocarbonconversion utilizing the present catalyst may be carried out as either avapor phase, a liquid phase or a mixed phase operation. Conversion maytake place in the absence or presence of hydrogen. Operation in thepresence of hydrogen is particularly advantageous for isomerization inpreserving catalyst life.

Isomerization of isomerizable hydrocarbons, such as naphthenes and/orparaffins, may be effectively carried out utilizing the catalyst of thisinvention. Thus, isomerization of straight chain or slightly branchedchain paraffins containing 4 or more carbon atoms per molecule, such asnormal butane, normal pentane, normal hexane, normal heptane, and normaloctane may be readily effected. Likewise, cycloparaffins containing atleast 5 carbon atoms in the ring, such as alkyl cyclopentanes andcyclohexanes may be effectively isomerized utilizing the presentcatalyst. It is contemplated that straight or branched chain saturatedhydrocarbons containing up to 30 carbon atoms or more per molecule maybe isomerized with the present catalyst, regardless of the source ofsuch hydrocarbons or mixtures containing the same. As examples ofcommercial mixtures, mention can be made of straight-run tops or lightnaphtha fractions which in various refineries are available in largeamounts.

In carrying out isomerization of isomerizable hydrocarbons utilizing thepresent catalyst, contact between the catalyst and hydrocarbon charge isconducted at a temperature between about 0° and about 200°C. andpreferably between about 20° and about 150°C. at a pressure betweenabout atmospheric and about 30 atmospheres or more. The hydrocarboncharge is passed over the catalyst at a liquid hourly space velocitygenerally between about 0.2 and about 10 and preferably between about0.5 and about 4. The resulting product is withdrawn from the reactionzone, separated from the reactor effluent and recovered by any suitablemeans such as fractional distillation. Any unreacted starting materialmay be recycled to form a portion of the feedstock.

The catalyst of this invention is also suitable for catalyzinghydrocarbon cracking. The hydrocarbon charge in such process maycomprise one or more normal paraffins or may be a complex mixture ofparaffins, naphthenes and aromatics, such as occurs in petroleum gasoil, which is the feedstock normally conducted to a commercial catalyticcracking unit. Hydrocarbon cracking utilizing the catalyst of thisinvention is essentially conducted at a temperature between about 400°and 650°C., a pressure of from about atmospheric to about 5 atmospheresand employing a liquid hourly space velocity of between about 0.5 andabout 100.

Alkylation employing the catalyst described herein may also beeffectively carried out. Thus, alkylation of an alkylatable hydrocarbonwith an olefin, alkyl halide or alcohol is desirably effected in thepresence of the catalyst of this invention at alkylation conditionsincluding a temperature of about 0° to about 150°C. and a pressure ofbetween about atmospheric and about 500 psig. The mole ratio ofalkylatable hydrocarbon to alkylating agent is preferably between about1:1 to about 10:1.

DESCRIPTION OF SPECIFIC EMBODIMENTS

The following examples will serve to illustrate the process of theinvention without limiting the same:

EXAMPLE 1

A catalyst containing 42.5% of antimony pentafluoride intercalated inthe lattice of graphite was prepared by drying a sample of graphite(20-65 mesh) in a vacuum oven for 2 days at 120°C. Ten grams of thedried graphite were then transferred to a 125 cc two-neck flask fittedwith a mechanical stirrer and a gas bag for maintaining a slightpositive pressure of nitrogen. Antimony pentafluoride (7.40 grams) wasrapidly weighed into the flask under nitrogen and the flask was thenflushed with dry nitrogen. The mixture was heated with occasionalstirring in an oil bath at 110°C. for a period of 1-3 days. No loss inweight or pressure increase occurred, indicating complete intercalationof the antimony pentafluoride.

A reactor was packed with 4 cc of this catalyst and placed in apressurized flow system. Dry cyclohexane containing 0.375 mole percentdissolved hydrogen was pumped at 4 cc/hour (LHSV = 1) upflow through thecatalyst bed maintained at 40°C. Conversion of cyclohexane tomethylcyclopentane increased gradually to 10 percent over a period of 25hours and remained constant at 10 percent for two hours. Suchcorresponds to 45 percent of the equilibrium conversion tomethylcyclopentane. The temperature was then raised to 50°C. Theconversion rapidly increased to 19 percent methylcyclopentane (73percent of the equilibrium conversion), remained constant at 19 percentfor 14 hours and then declined slowly. The temperature was thenincreased to 60°C. The conversion rapidly increased to 24 percentmethylcyclopentane (80 percent of the equilibrium conversion), remainedconstant at 24 percent for 4 hours and thereafter declined slowly to 2percent over a period of 18 hours.

EXAMPLE 2

A catalyst containing 42.5% of antimony pentafluoride and 0.3% platinumintercalated in the lattice of graphite was prepared by adding anaqueous solution of chloroplatinic acid containing 0.136 gram ofplatinum to 25 grams of 20-65 mesh graphite. The water was thendistilled off under vacuum. The resulting product was dried for 2 hoursat 130°C. in a stream of dry nitrogen. The chloroplatinic acid was thenintercalated by heating the product at 150°C. for approximately 4 hoursin the presence of chlorine. The platinum was then reduced by contactwith hydrogen at 450°C. for eight hours. Antimony pentafluoride was thenloaded as described in Example 1 to yield a final catalyst containing0.3 weight percent platinum and 42.5 weight percent antimonypentafluoride.

A reactor was packed with 4 cc of this catalyst. Dry n-hexane containing1.75 mole percent dissolved hydrogen was pumped at a liquid hourly spacevelocity of 1 upflow through the catalyst bed maintained at 40°C. Theconversion of n-hexane to products increased rapidly to 50 percent,remained constant for 3 hours and then declined slowly. The temperaturewas raised to 60°C. whereupon the conversion of n-hexane rapidlyincreased to 65 percent.

The product distribution at 4.3 hours on-stream is shown below:

                  Product Distribution                                            ______________________________________                                        Hydrocarbon           %                                                       ______________________________________                                        Propane               0.4                                                     2-Methylpropane       10.2                                                    n-Butane              2.4                                                     2-Methylbutane        20.2                                                    n-Pentane             3.4                                                     2,2-Dimethylbutane    10.9                                                    2,3-Dimethylbutane/   19.9                                                    2-Methylpentane                                                               3-Methylpentane       7.8                                                     Methylcyclopentane    0.4                                                     2,2-Dimethylpentane   2.5                                                     2,4-Dimethylpentane   0.9                                                     2,2,3-Trimethylbutane 0.5                                                     3,3-Dimethylpentane   4.9                                                     Cyclohexane           1.9                                                     2-Methylhexane        4.0                                                     2,3-Dimethylpentane   0.1                                                     3-Methylhexane        0.1                                                     3-Ethylpentane        0.8                                                     C.sub.8 .sup.+        8.7                                                     ______________________________________                                    

EXAMPLE 3

A catalyst containing 42.5% SbF₅ but no platinum was prepared and testedfor n-hexane isomerization according to Example 2. Comparison ofn-hexane conversions and the ratio of isomerization to cracking atmaximum conversion in the presence and absence of platinum shows adistinct advantage in having platinum present.

    ______________________________________                                                                  Isomerization/                                      Time On-Stream                                                                          n-Hexane Conversion                                                                           Cracking Platinum                                   (Min.)    0.3%      0% Pt.    0.3%   0% Pt.                                   ______________________________________                                        30        52        26                                                        60        54        22        2.02   0.651                                    90        32         8                                                        120       24         4                                                        ______________________________________                                    

EXAMPLE 4

A catalyst containing 31% aluminum chloride and 1.5% platinumintercalated in the lattice of graphite was prepared by adding anaqueous solution of chloroplatinic acid containing 0.547 grams ofplatinum to 25 grams of 20-65 mesh graphite. The water was thendistilled off under vacuum and the resulting product dried for two hoursat 130°C. in nitrogen. The chloroplatinic acid was then intercalated byheating the product at 150°C. for about 4 hours in the presence ofchlorine. The platinum was then reduced by contact with hydrogen at450°C. for 7 hours to yield a platinum/graphite intercalation compoundcontaining 2.1 weight percent platinum. This compound (8.63 grams),together with aluminum chloride (3.93 grams) were weighed under nitrogeninto a 125 cc two-neck flask fitted with a mechanical stirrer and a gasbag for maintaining a slight positive pressure. The flask was flushedwith chlorine and heated at 110°C. for 21 hours with occasionalstirring. The aluminum chloride intercalated readily to yield a catalystcontaining 31 weight percent aluminum chloride and 1.5 weight percentplatinum.

A reactor was packed with 4 cc of the above catalyst and placed in apressurized flow system. Dry n-hexane, saturated with hydrogen at 465psi and containing 0.2 weight percent t-butyl chloride was pumped upflowat a liquid hourly space velocity of 2 through the catalyst bedmaintained at 40°C. Isomerization, cracking and alkylation wereobserved. Conversion of n-hexane to products increased rapidly to 56percent and then decreased over 100 cc to 5 percent. Cracking andalkylation decreased relative to isomerization over this interval.Increasing the temperature to 60°C. raised the conversion to 11 percent.The n-hexane feed was next saturated with hydrogen at 700 psi and thereactor temperature was raised to 80°C. The conversion increased to 15percent. After 192 cc of n-hexane, the temperature was raised to 100°C.,with a doubling of the conversion to 31 percent. Thereafter, theconversion slowly dropped to 25 percent. After 292 cc, the temperaturewas raised to 120°C. The conversion increased from 25 percent to 32percent. After 388 cc, the temperature was raised to 140°C. Theconversion increased from 29 to 53 percent and remained at this leveluntil the experiment was terminated after 408 cc. Results are summarizedin Table I below.

                                      TABLE I                                     __________________________________________________________________________                                        2,3-                                                                          Dimethyl-                                                                     butane                                                                  2,2-  2-    3-                                  Cubic       iso-                                                                              n-  iso- n-   Dimethyl-                                                                           Methyl-                                                                             Methyl-                                                                            n-                             Centimeters                                                                          Propane                                                                            Butane                                                                            Butane                                                                            Pentane                                                                            Pentane                                                                            butane                                                                              pentane                                                                             pentane                                                                            Hexane                                                                            C.sub.7 .sup.+                                                                    T°C                                                                        LHSV               __________________________________________________________________________     8     Trace                                                                              9.5 0.4 12.0 1.7  3.3   11.4  4.2  44.0                                                                              13.3                                                                               40 2                  100    Trace                                                                              0.8 Trace                                                                             0.9  Trace                                                                              0.1   1.8   0.7  95.0                                                                              0.7  40 1                  116    Trace                                                                              1.5 0.1 1.8  0.1  0.2   3.9   1.5  89.5                                                                              1.4  60 1                  192    0.1  1.9 0.1 2.3  0.3  0.3   5.6   2.4  85.3                                                                              1.8  80 1                  212    0.4  3.9 0.5 5.1  0.7  0.7   10.8  4.9  69.5                                                                              3.4 100 1                  292    0.4  3.2 0.4 3.7  0.6  0.5   9.2   4.2  75.3                                                                              2.4 100 1                  312    0.7  3.8 0.7 4.9  0.8  0.7   11.6  5.5  67.8                                                                              3.4 120 1                  388    0.3  2.7 0.5 3.8  0.9  1.0   12.3  5.5  70.8                                                                              2.4 120 1                  408    0.8  5.0 1.2 8.0  1.8  2.2   20.2  7.8  47.1                                                                              5.8 140 1                  __________________________________________________________________________

The following two examples furnish a comparison of catalysts whereinantimony pentafluoride is (1) deposited on and (2) intercalated ingraphite.

EXAMPLE 5

A catalyst of antimony pentafluoride deposited on graphite was preparedby adding 5 grams of graphite to a solution of 7.50 grams of antimonypentafluoride in 25 cc of liquid SO₂ at -30°C. stirring for 2 hours andthen filtering rapidly under dry nitrogen. The product was transferredunder nitrogen to a flask and evacuated at 100 mm mercury to removeresidual SO₂. The vacuum was broken by bleeding in dry nitrogen.

To a reactor containing 0.5 cc (0.59 gram) of the above catalyst undernitrogen was added 4 cc of cyclohexane (freshly percolated throughalumina). The mixture was placed in an oil bath at 40°C. and wasstirred. Aliquots of the hydrocarbon layer were taken as a function oftime and analyzed by gas chromatography. The results obtained arehereinafter summarized in Table II.

EXAMPLE 6

A catalyst of antimony pentafluoride intercalated in graphite wasprepared by heating 15 grams of antimony pentafluoride with 10g of (PGR4/30/74) graphite at 110°C. for 2.7 days under nitrogen. This catalystwas tested as in Example 5 at 40°C. for cyclohexane isomerization. Theresults obtained are summarized below in Table II.

                  TABLE II                                                        ______________________________________                                                         % Methylcyclopentane                                         Temp.  Time     Effective  SbF.sub.5 on                                                                           SbF.sub.5 in                              (°C)                                                                          (Hr)     LHSV       Graphite Graphite                                  ______________________________________                                        40      2       4          0.4      12                                        40      4       2          0.6      13                                        40     24       0.33       0.9      13                                        ______________________________________                                    

As will be evident from the above results, the catalyst in whichantimony pentafluoride was intercalated in the graphite was vastlysuperior to the catalyst in which antimony pentafluoride was depositedon the graphite.

The following two examples furnish a comparison of catalysts whereinHSbF₅ SO₃ F is (1) deposited on and (2) intercalated in graphite.

EXAMPLE 7

A catalyst of HSbF₅ SO₃ F deposited on graphite was prepared by adding 5grams of graphite to a solution of SbF₅ (7.50 grams) and HSO₃ F (6.93grams) in 25 cc of liquid SO₂ at -30°C. The mixture was thereafterprocessed and the product tested for cyclohexane isomerization asdescribed in Example 5. The results are hereinafter summarized in TableIII.

EXAMPLE 8

A catalyst of HSbF₅ SO₃ F intercalated in graphite was prepared byadding 3 grams of SbF₅ intercalated in 2 grams of graphite to a solutionof HSO₃ F (2.77 grams) in 10 cc of liquid SO₂ at -30°C. After stirringfor 2 hours and processing under conditions described in Example 5, theproduct was tested for cyclohexane isomerization. The results obtainedare summarized in Table III below.

                  TABLE III                                                       ______________________________________                                                         % Methylcyclopentane                                         Temp.  Time     Effective  HSbF.sub.5 SO.sub.3 F                                                                  HSbF.sub.5 SO.sub.3 F                     (°C)                                                                          (Hr)     LHSV       on Graphite                                                                            in Graphite                               ______________________________________                                        40      2       4          0.035    5.9                                       40      4       2          0.036    6.6                                       40     24       0.33       0.052    7.2                                       ______________________________________                                    

It will be evident from the above results that the intercalated catalystafforded considerably higher conversion to methylcyclopentane ascompared with the catalyst in which HSbF₅ SO₃ F was deposited on thegraphite.

EXAMPLE 9

A catalyst of HSbF₅ SO₃ F and Pt both intercalated in graphite wasprepared by adding 1.91 grams SbF₅ and 0.054 gram Pt intercalated ingraphite to a solution of HSO₃ F (0.88 gram) in 10 cc of liquid SO₂ at-30°C. After stirring for 2 hours, the SO₂ was distilled. The productwas evacuated at 100 mm Hg to remove residual SO₂. The vacuum was brokenby bleeding in dry nitrogen.

The product was tested for cyclohexane isomerization according toExample 1. The results obtained are summarized below in Table IV.

                  TABLE IV                                                        ______________________________________                                        Time On-Stream   Percent                                                      (Hrs.)           Methylcyclopentane                                           ______________________________________                                        0                .06                                                          1                0.15                                                         2                0.85                                                         3                0.53                                                         4                0.39                                                         5                0.34                                                         ______________________________________                                    

It is to be understood that the foregoing description is merelyillustrative of preferred embodiments of the invention of which manyvariations may be made by those skilled in the art within the scope ofthe following claims without departing from the spirit thereof.

I claim:
 1. A process for effecting alkylation of a normal paraffinwhich comprises contacting said normal paraffin under alkylationconditions with an alkylating agent selected from the group consistingof olefin, alkylhalide and alcohol with a catalyst consistingessentially of graphite having intercalated in the lattice thereofbetween about 5 and about 75 weight percent of a Lewis acid consistingessentially of a halide of an element of Group IIA, IIIA, IVB, V or VIBand between about 0.1 and about 20 weight percent of a Group VIII metal.2. The process of claim 1 wherein said alkylation conditions include atemperature between about 0°C and about 150°C, a pressure between aboutatmospheric and about 500 psig and a mole ratio of said normal paraffinto said alkylating agent between about 1:1 and about 10:1.
 3. Theprocess of claim 1 wherein said Lewis acid is antimony pentafluoride. 4.The process of claim 1 wherein said Lewis acid is aluminum chloride. 5.The process of claim 1 wherein said Group VIII metal is platinum.
 6. Theprocess of claim 1 wherein said alkylation is carried out in thepresence of hydrogen.